South American hemorrhagic fevers
Rapidly emerging viral diseases

Viral hemorrhagic fevers are are a group of infectious diseases with similar symptoms in people. Viruses affect the vascular system and can produce severe multi-systemic illnesses in some. The illnesses are usually associated with high mortality. Of specific concern are the hemorrhagic fevers caused by viruses in South America. They are rapidly expanding in territory and affecting more people every year.

How many people are infected each year is unknown, some may be asymptomatic and screening for these diseases is not routinely performed.

?

PEOPLE

New infections per year

/

25

%

Mortality

/

?

PEOPLE

Dead per year

What causes South American hemorrhagic fevers

South American hemorrhagic fevers are caused by a group of arenaviruses of which Lassa fever virus (a West African virus) is probably the most well known species. They all have rodent reservoir hosts, with humans merely being accidental hosts. Many arenaviruses have more than one rodent host, although usually a single species will predominate as the reservoir in nature.

There are more than 20 recognized members of the Arenaviridae, but fewer than half of these viruses have been linked to human illness. In South America, 5 arenaviruses are know to cause hemorrhagic fevers: Junin virus, Machupo virus, Chapare virus, Guanarito virus and Sabiá virus.

It is entirely possible more arenaviruses, that we are yet unaware of, can cause significant disease in humans.

Photo: The common house mouse, a vector of Junin virus

Where are South American hemorrhagic fevers found

Each arenavirus is maintained in one or a few animal reservoir hosts, and is limited by the distribution of that host. The occurrence of these viruses is patchy, with higher infection rates among the rodents in hot spots.

Junin virus occurs in central Argentina, Machupo and Chapare viruses in Bolivia, Guanarito virus in western Venezuela, and Sabia virus in Brazil. In each case, the disease tends to occur in a limited region of the country.

Since the discovery of Argentinian Junin virus in 1958, the geographical distribution of the pathogen, although still confined to Argentina, has expanded significantly from 15 000 km2 to 150 000km2 in the year 2000. Likewise, for Machupo virus in Bolivia there are concerns about the expansion of the virus to other provinces outside the endemic regions of the Mamoré and Iténez provinces.

Image: Geographical distribution of South American hemorrhagic fevers

What are the symptoms of South American hemorrhagic fevers

Arenavirus infections become apparent in approximately one to three weeks but can be shortened to just two days when exposed to large amounts of virus. They may be completely asymptomatic or mild to fatal. The symptoms of the disease can be confusing, the onset is flu-like with fever, malaise, headache and myalgia. Some patients recover, while others develop more severe symptoms. Petechiae (blood spots) on the skin and bleeding from the nose and gums are observed when the disease progresses to the hemorrhagic phase. Ultimately, severe hemorrhagic symptoms, frequently combined with neurological issues will develop, along with edema, hypo-tension and circulatory collapse. Person-to-person spread is possible.

Junin virus has a mortality rate between 20 and 30 percent. Machupo virus between 5 to 30 percent. Guanarito virus around 23 percent.

How can South American hemorrhagic fevers be prevented

Deforestation and human encroachment into rodent habitats are likely the main drivers behind infections.

These viruses are spread mostly by inhalation of aerosolized droplets of saliva, respiratory secretions, urine, feces or blood from infected rodents. Frequently people will be infected by contaminated dust that is kicked up. Activities such as sweeping, dusting and vacuuming should be avoided in areas where mouse droppings are found. Arenaviruses can be inactivated by most detergents and disinfectants including bleach. Spaying surfaces where mouse droppings are found minimizes the risk of infection.

In Argentina, many infections have been associated with corn harvesting. In other countries, infections are frequently related to agriculture.

Special attention needs to be paid when caring for patients who are infected. Some of these diseases have also been involved in laboratory accidents. There has also been interest in these viruses for bio-warfare.

Investigational vaccines exist for Argentine hemorrhagic fever. The Junin vaccine, is licensed in Argentina to be used in regions where the virus is endemic or for people who work in laboratories and frequently come into contact with these viruses. Some cross reactivity may exist for the other viruses in this group.

How are South American hemorrhagic fevers diagnosed

Arenaviruses can be detected by Polymerase chain reaction (PCR) tests, such as the ones made available by the WoIDM. There is there is
limited clinical experience with these assays.

How are South American hemorrhagic fevers treated

Supportive treatment is used for all South American hemorrhagic fevers.

The antiviral drug ribavirin has been used in some cases. Treatment is most effective when it is started early in the course of the disease. Clinical experience is limited and only anecdotal reports are available.

Human immune plasma is used to treat Argentine hemorrhagic fever (Junin virus). and plasma banks have been established. Treatment is most effective if it is started soon after the onset of the clinical signs. This option does not exist for other South American arenaviruses.

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